1. Field of the Invention
The present invention relates to communication techniques of sending/receiving a request and a response between communication devices.
2. Related Art
Nowadays, communication devices such as personal computers and network appliances perform communication with other communication devices based on various protocols. For example, communication between communication devices is performed by using various networks such as the Internet and a LAN (Local Area Network), or various hardware interfaces.
POP3 (Post Office Protocol version 3, RFC 1939) is known as such a protocol that is used in communication between communication devices.
Communication between communication devices based on a protocol such as POP3 is conducted by one communication device sending a request and the other communication device returning a response to the request.
POP3 is described in detail in the following:
J. Myers, “RFC 1939-Post Office Protocol (POP) Version 3”, [online] May 1996, IAB (Internet Architecture Board) standard recommendation RFC (Request for Comments), [searched on Apr. 3, 2006]<URL: http://www.ietf.org/rfc/rfc1939.txt>.
In communication between communication devices based on a protocol such as POP3, if a response to a request has an error, that is, if data that does not conform to a procedure or format prescribed by the protocol is returned as a response, a communication device that sends the request terminates communication processing for the occurrence of the error.
For instance, in the case where the protocol is not implemented strictly in a communication device that receives the request or part of the implemented protocol contains a bug, the communication device will end up returning a wrong response to the request. Whenever this happens, error termination occurs in the communication between the communication devices.